"the number of Americans who self-identify as Cherokee or mixed-race Cherokee has grown substantially over the past two decades."

Assuming completely random mating, the ancestor count of a small group inside a large stable population should double every generation.

"In 2000, the federal Census reported that 729,533 Americans self-identified as Cherokee. By 2010, that number increased, with the Census Bureau reporting that 819,105 Americans claiming at least one Cherokee ancestor."

12% in 10 years, or 33% in 25 years (a modern generation) is less than would be expected by that first-order theory.